An engine of a hybrid vehicle may be periodically stopped to conserve fuel. The engine may be restarted when driveline torque is desired to accelerate or keep the vehicle moving. However, restarting the engine simply based on an increasing torque demand may not provide a desirable torque response during some conditions. For example, during conditions where a driver applies a constant accelerator pedal position, torque converter impeller torque demand falls as the vehicle accelerates in a first gear and then rises as a result of an upshift to a second gear where transmission multiplication is reduced. Consequently, it may be possible to meet desired driveline torque with the engine off and a driveline disconnect clutch open before an upshift, but the desired driveline torque may not be possible without operating the engine after the upshift.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of starting an engine, comprising: predicting a desired torque after a transmission upshift; and starting rotation of a stopped engine if the predicted desired torque after the transmission upshift is greater than a threshold amount of torque.
By predicting a driveline torque requirement after a scheduled shift, it may be possible to start an engine and have the engine prepared to provide torque to the driveline as a transmission upshifts. Consequently, engine torque may be available to the driveline so that driveline torque is not reduced after an upshift.
The present description may provide several advantages. Specifically, the approach may improve driveline torque response. Further, the approach may provide more reduce the possibility of noticeable driveline torque reductions during gear shifting. Further still, the approach may improve vehicle fuel economy by allowing the engine to be stopped rather than waiting at idle to provide torque after a transmission gear shift.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.